1. Field of the Invention
The present invention relates generally to a vibration damping device used for an automotive engine mount or the like, and particularly to a fluid-filled type vibration damping device that utilizes vibration damping effect based on the flow behavior of the fluid sealed in the fluid chamber, and to a method for manufacturing such a device.
2. Description of the Related Art
There have been known fluid-filled type vibration damping devices including a fluid chamber filled with a non-compressible fluid and capable of attaining vibration damping effect by utilizing flow behavior of the fluid induced during input of vibration. In the fluid-filled type vibration damping device, a first mounting member and a second mounting member are elastically connected by a main rubber elastic body, and the main rubber elastic body partially defines a wall of the fluid chamber, in order to apply vibration to the fluid chamber. Also, in recent years, with the aim of realizing more enhanced vibration damping characteristics, proposed is an active type fluid-filled vibration damping device furnished with an electromagnetic actuator and able to actively control pressure in the fluid chamber (see Japanese Unexamined Patent Publication No. JP-A-2005-273682).
The fluid-filled vibration damping device of this type employs a structure in which the second mounting member is divided into a base component of metal and a tubular mating component of metal, and the tubular mating component is externally fitted onto the outer circumferential face of the base component by means of a diameter-constricting caulking with a sealing rubber clasped therebetween, making it possible to seal the non-compressible fluid or attach the electromagnetic actuator. With this structure, the sealing rubber is interposed at the mate-fastened portion and caulked by the diameter constriction, thereby ensuring fluidtightness of the fluid chamber and to prevent dust from coming into the interior of the electromagnetic actuator.
However, the sealing rubber clasped at the mate-fastened portion posed a problem of difficulty in controlling a level of the diameter constriction during the diameter-constricting caulking. For example, an excessive deformation on the sealing rubber poses a risk of adverse effect on its durability. On the other hand, a poor compression on the sealing rubber poses a risk of insufficient sealing performance. In addition, due to variability in the level of the diameter constriction, there is also a risk that accuracy of coaxiality or parallelism of the base component and the tubular mating component may deteriorate.
In particular, with respect to the active type fluid-filled vibration damping device, a higher degree of accuracy of coaxiality or parallelism and durability of the device is required in order to efficiently transmit oscillation force at the connecting section of the base component and the tubular mating component which provides a support portion of the electromagnetic actuator. Accordingly, more enhanced dimensional accuracy, fastening strength, as well as durability at the mate-fastened portion have been desired, while at the same time ensuring its sealing performance.